re: Poker & Showing Cards?
I know in the WSoP
you are not allowed to show your cards like that. Daniel Negreanu likes to talk about what a silly rule that is.
The reason you are no allowed to show cards before deciding to call or fold is to prevent collaboration. Players can dump chips to each other.
Let's say Player A and Player B are friends. The tournament is on the bubble with 100/200 blinds. Player A shoves on the button for his last 600 chips. Player B is in the BB with 9,600 chips.
Player B looks down and sees K/9.
Theoretically, B could want to help assure that his buddy makes the money. Player B then exposed his K/9. His buddy gives him a "please fold I'm beat" signal and then player B mucks the hand, giving Player A a small win which won't guarantee that he makes the money. Or alternatively, he could give him a "yeah I can beat that, please call" signal which gives Player A an excellent chance of doubling up and finishing in the money.